1. Field of the Invention
The present invention relates generally to materials and methods for rapid and efficient preferential binding of chemical functional groups to surface reactivity templates (see below) formed by patterned irradiation of polymer films. In particular, the invention describes binding materials and processes which (i) can be carried out using safe solvents (e.g., water and simple aliphatic alcohols having 3 or fewer carbon atoms), (ii) are applicable to surfaces of polymer films of average thickness greater than one monolayer (i.e., thicknesses greater than xcx9c0.5 nm), (iii) include either covalent or non-covalent (e.g., electrostatic, van der Waals, etc.) modes for binding the desired functional group(s) to the selected portion of the reactivity template formed on the polymer film surface, and (iv) permits preferential binding of the desired functional group to either the reactivity template created at the polymer film surface as a result of exposure of the film to patterned actinic radiation (thereby ultimately creating a negative tone image of the attached functional group) or that region of the polymer film left unexposed and unchanged during the aforementioned patterning process (thereby ultimately creating a positive tone image on the polymer surface).
2. Description of the Related Art
During the last several years, there has been an interest in exploring, developing, and continually refining the concept of surface reactivity templates. A reactivity template is a well-defined region of controlled dimensions and placement on a substrate surface where the chemical and/or physical properties of the region differ from the properties found elsewhere on the surface. One general scheme for the fabrication of reactivity templates is illustrated using organosilane thin films in FIG. 1. A substrate whose surface has at least some hydroxyl groups is treated with a solution of an organosilane of general formula RnRxe2x80x2mSiX(4xe2x88x92nxe2x88x92m) (where X is a halide or pseudohalide, R and Rxe2x80x2 are organic functional groups with n, m integersxe2x89xa70 such that 1xe2x89xa6(n+m)xe2x89xa63; cases most often encountered are those for which n=1, m=0 (shown in FIG. 1) or n=1, m=2, Rxe2x80x2=CH3). For substrates which do not intrinsically possess surface hydroxyl groups, chemical or plasma treatments may generate the requisite surface xe2x80x94OH sites prior to the organosilane treatment. Chemisorption of the organosilane species onto the substrate surface occurs via reaction between the Sixe2x80x94X bond and surface xe2x80x94OH group; elimination of HX occurs with the formation of a strong Sixe2x80x94Oxe2x80x94 Substrate covalent bond. Following reaction with the organosilane, the chemical and physical properties of the surface reflect those of the homogeneous organosilane film covering, rather than those of the original substrate surface.
Accordingly, it is an object of this invention to provide improved substrate patterning, using environmentally friendlier materials than had been available using the techniques of the prior art.
The objects of the invention are accomplished by the structures and processes hereinafter described.
An aspect of the present invention is a process for modifying a substrate in areas that are exposed to actinic radiation, having the steps: (a) providing on the substrate functional groups adapted for conversion to oxygen-containing photoproducts upon exposure to actinic radiation; (b) exposing at least a portion of the substrate to the actinic radiation, converting the functional groups in an exposed region of the substrate to the photoproducts; (c) contacting the photoproducts with a primary or secondary amine in the presence of hydrogen ions, forming imine groups; and (d) contacting the imine groups with a reducing agent, forming amine groups on the substrate in the exposed region.
Another aspect of the present invention is a process for modifying a substrate in areas that are unexposed to actinic radiation, having the steps: (a) providing on the substrate aryl functional groups adapted for conversion to oxygen-containing photoproducts upon exposure to actinic radiation; (b) exposing a portion of the substrate to the actinic radiation, converting the aryl functional groups in an exposed region of the substrate to the photoproducts, and not converting the aryl functional groups in an unexposed region of the substrate to the photoproducts; (c) contacting the aryl functional groups in the unexposed region of the substrate with a compound adapted for physisorption to the aryl functional groups, preferentially physisorbing the compound onto the substrate in the unexposed regions.